Merge 'sybase_computed_columns' into 'trunk'

r22895@hlagh (orig r8473):  caelum | 2010-01-30 03:57:26 -0500
branch to fix computed columns in Sybase ASE
r22911@hlagh (orig r8489):  caelum | 2010-01-31 07:18:33 -0500
empty insert into a Sybase table with computed columns and either data_type => undef or default_value => SCALARREF works now
r22912@hlagh (orig r8490):  caelum | 2010-01-31 07:39:32 -0500
add POD about computed columns and timestamps for Sybase
r22918@hlagh (orig r8496):  caelum | 2010-02-01 05:09:07 -0500
update POD about Schema::Loader for Sybase